According to JAL, tape covering two holes used to regulate airflow in case of gas generated during battery fault was inadvertently not removed after pre-flight testing. That lead to an indicator begin activated showing the difference in pressure between the inside and outside of the auxiliary power unit's (APU) battery enclosure box.

The issue with the battery resulted from maintenance oversight, and not a direct issue with the battery itself, JAL said. The airline took precautionary measures by replacing the 787 with a 767 so that the flight could be resumed without causing too much of a delay.

"As the result of the inspection, no battery failure was observed," JAL said in a statement. "The relevancy between holes obscured by tape and the indicator activation is under investigation. This situation does not affect the battery system function or the gas venting function."

The carrier had flown the affected 787 twice the day before without any issues.